Hydrogen and Helium Edge-Plasmas

Transcription

1 Hydrogen and Helium Edge-Plasmas Comparison of high and low recycling T.D. Rognlien and M.E. Rensink Lawrence Livermore National Lab Presented at the ALPS/APEX Meeting Argonne National Lab May 8-12, 2

2 Outline 1. High- and low-recycling hydrogen plasmas 2. ARIES-RS results 3. Helium spatial concentrations

3 High and low recycling have similar plate heat flux profiles ITER-like geometry with 15 MW into SOL Heat flux to plate (MW/m**2) 8 4 R = 1 R is particle recycling coeff. R =.5 1-D plasma pressure balance is broken by radial transport for R=.5 case Distance from separatrix at plate (cm) 2 Electron temperature (ev) 1 R =.5 n ~ 1/T e R = Distance from separatrix at plate (cm)

4 Edge plasma changes from low to high recycling Ion parallel velocity (km/s) 8 4 Ion parallel velocity v for high recycling (R=1).1 x v for low recycling (R=.25) Electron temperature in SOL (ev) 4 2 Electron temperature Low recycling High recycling X-point Poloidal distance (m) Top of machine Divertor plate

5 Low recycling yields hot edge plasma unless there is very large DT particle fueling Separatrix electron temperature (ev) Low recycling, R=.25 T e 4 8 n i Core DT particle fueling current (ka) Separatrix density (1 1/m )

6 Mesh obtained for standard ARIES-RS with symmetric double-null divertor 8 Symmetry plane Inner divertor Outer divertor

7 Small modification to poloidal B-field coils used to produce single-null configuration 4 Resulting divertor plasma parameters given in a memo

8 Low recycling hydrogen can give much better helium compression in divertor 21 1 Ion density (m -3 ) R =.99 DT R =.99 He Helium D-T High DT recycling D-T Ion density (m -3 ) R =.5 DT R =.99 He Low DT recycling Helium 1 17 X-point Poloidal distance from top (m) Orthogonal plate

9 Helium flux displaced toward outer wall for vertical divertor plate 1% helium at the core-edge boundary R_hydrogen =.5, R_helium =.95 Orthogonal divertor plate Vertical divertor plate Particle flux normal to plate (1/s m**2) Separatrix D-T D-T + Particle flux normal to plate(1/s m**2) Separatrix D-T + D-T Particle flux normal to plate (1/s m**2) He ++ Helium He + Particle flux normal to plate(1/s m**2) Helium He + He ++ Distance along divertor plate (m) Distance along divertor plate (m)

10 Helium ion density concentrates near wall for vertical divertor plate 17-3 R =.5, R =.99, n at core boundary = 4 x 1 m DT He He Vertical position (m) 4 3 Orthogonal divertor plate Helium density vertical position (m) 4 3 Helium density Vertical divertor plate Major radius (m)

11 Helium gas density also concentrates near wall for vertical plate 2.6 Vertical position (m) He gas density Orthogonal plate Vertical position (m) He gas density Vertical plate Major radius (m)

12 Summary 1. High- and low-recycling hydrogen plasmas - poloidal flow toward divertor much reduced for high recycling plamas - major impact on impurities - edge density for low recycling is controlled by fueling; more analysis of cases with low edge density needed 2. ARIES-RS results - an MHD equilibrium for single null now available - divertor plasma weakly attached assuming 9% of core power radiated; strongly attached otherwise 3. Helium spatial concentrations - low recycling with large fueling causes large helium densities near the plate - enhances duct pumping - tilted divertor plate forces helium toward outer wall